Once brown on all sides, place the tenderloin in the slow cooker and turn it to low. In a small saucepan, combine cranberries, water, and maple syrup and bring to a boil. You will want to cook this for about 5 minutes or until cranberries begin to split.

Then pour over the tenderloin in the slow cooker. Place the sprig of fresh rosemary on top of pork tenderloin and cover. Cook your pork tenderloin with cranberry sauce on low for 4-5 hours. Remove from the slow cooker when the internal temperature is 145 degrees. Let rest 10 minutes before slicing. Serve with reserved ½ cup cranberry sauce on top and additional orange zest, if desired.